Electric signaling system



June 15,1926. 1,589,071

' W. .HAHNLE ELECTRIC SIGNALING SYSTEM I Filed Jan. 15, 1922 via. 4%

Patented W is; 1926.

UNITED STATES PATENT OFFICE.

WALTER HKHNLE, OF DEGERLOCH, STUTTGART, GERMANY, ASSIGNOR TO ROBERT BOSCH AKTIENGESELLSCHAFT, F STUTTGART, GERMANY.

ELECTRIC SIGNALING SYSTEM.

Application filed January 13, 1922, Serial No. 529,093, and. in Germanyqoctober 17, 1921.

It is desirable that sound signaling instrumen'ts intended for use onmotor vehicles be made capable of producing a powerful and penetrating sound when the 6 vehicle is operated, particularly at a rapid rate of speed, upon an 0 en road, whereas in towns a more agreea 1e and less loud sound is desired.

With electrical sound signaling instruments operated by electromagnets excited by periodically interrupted continuous current the change and the weakening of the sound has hitherto been efiected by insert- 7 ing an ohmic resistance into the circuit of 15. the electromagnet. This procedure entails, however; the drawback that the instrument sometimes entirely fails to sound the signal even when the voltage of the source of current has not dropped so low as to be insufficient for operating the instrument. It is obvious that accidents may be caused by such a default.

The object of the present invention is to obviate that drawback, and I attain this effeet by employingas a series impedance for the electromagnet a choking coil instead of an ohmic resistance.

The failure of the signaling instrument if an ohmic resistance is used is caused'by the weakening of the current by the ohmic resistance previous to its initial flow through the bobbin of the electromagnet, the result being an insufficient energization of the electromagnet to initially move the armature tional resistance and the acceleration resistance or mertia of the armature to be overcome upon its initial movement are greater than the resistances arising or existing during its continued movements in service. If, however, a" suifici'ent initial flow of current is provided to begin the oscillations of the armature, then the current and, thus, the attracting power of theelectromagnet may be greatly weakened without a complete interruption of the buzzer. action.

A choking coil has, 'as is known, the property of letting an uninterrupted continuous current pass without hindrance, whereas an interrupted continuous current is choked at a gradually increasing rate according to the 4 increase in the number of interruptions. If, therefore, a choking coil is inserted into the from its position of rest, because the fric-' tromagnet of the full strength of the curthis moment a periodically interrupted current flows through the choking coil, whereby the current is correspondingly weakened. The sound which the signaling instrument produces is, therefore, reduced in ,volume and its pitch and tone-color or timbre are altered. Failure of the instrument is excluded because the buzzer play commences only upon an initial flow through the elecrent. On the other hand, the signaling instrument does not produce a sharp initial tone because only the first attraction of the argiature takes place with the full amplitu e. v

In order to more fully explain my invention, I refer to the accompanying drawing,

which shows,.by way of example in Fig. 1, "21' dia rammatlcally drawn axial section throng a motor-car horn, in connection with an electrifcircuit and the appertaining apparatus, the motor car being' indicated in its outlines by thin full lines and on "a g'reatly reduced scale. In Fig. 2 I have shown a' modified 'wiring diagram embody- 'ing my invention.-

The diaphragm. 1 of the horn is directly connected with the armature 2 of an electro ma et 3. The armatureoperates also the ma e-and-break; or buzzer contacts 4 for the service current. 6 and (are two switching devices, mews branches 10 and 11. respectively of the circuit. Both branches 10 and lllare 'arran edi'n series with the electro-Inagnet,'the u'zzer contacts 4'and the source "of current 5, forming a circuit but the former is arranged to be closed over the switch 6- for emitting a; powerful sound, while the latter is arranged to be closedcby switch 7 to include the rea'ctance or choking coil 8 to produce a reduced sound.

circuit is closed. When the circuit is closed.

by the switch 6 the horn will be operated at full power. When the choking coil is cut into the circuit by closing the switch 7, the full initial flow of current energizes the electromagnet which then attracts the armature 2 with its full power. But immediately thereafter the buzzer contacts are repeate dly opened and closed and the continuous current is now periodically interrupted whereby the self-induction of the choking coil is made to weaken the service current so that the sound produced by the signaling instrument is correspondingly reduced.

The invention may be employed also in connection with such signaling instruments in which the sound-producing diaphragm is operated not directly by the electromagnet, but, for instance, by the mediation of an air-pump constructed as a diaphragm-pump and driven by the electromagnet.

Instead of two parallel branches of circuit, each controlled by a switch as illustrated in Fig. 1, a switch 6 may be arranged in the unramified part of the circuit as shown in Fig. 2. In one of the two branches of'the circuit is arranged a switch 9 while the other branch contains the choking coil only. By opening or closing the switch 9,

the choking coil is thrown into or out of action.

Having now described my invention, what I claim as new and desire to secure by Letters Patent of the-United States is:

1. An electrically operated signaling system comprising, in combination, a signaling instrument having sound producing means, an electromagnet adapted to operate said sound producing means, an energizing circuit for said electromagnet having a source of continuous current and a current interrupter operable by said electromagnet, a manually operable circuit opening and closm switch in said circuit, a shunt around said switch, a choke coil in said shunt and a circuit opening and closing switch in said shunt.

2. An electrically operated signaling system comprising, in combination, a signaling instrument having sound producing means, an electro-magnet adapted to operate said sound-producing means, an energizing circuit for said electro-magnethaving a source of continuous current and a current-interrupter operable by said electro-magnet, means for manually opening and closing said circuit, a choking coil and means for switching said choking-coil into or out of said circuit.

In testimony whereof I have aflixed my signature. 

